Many engineering components comprise metal housings containing passages. The passages are usually cylindrical and may be formed by methods such as drilling. It is often necessary to intersect such passages, so that one passage intersects with another passage at an intersection or transition.
One problem often encountered when designing and using such components is that stress concentrations can arise at the intersections or transitions when the passages are under internal pressure. For example, in hydraulic applications such as pumps, the passages carry high-pressure fluid which acts upon the walls of the passages to create high stress concentrations, which can lead to failure of the component by fracture or deformation close to or at the intersection. In some applications, such as common rail fuel pumps, the stresses generated at such intersections can be extremely high due to the considerable pressure of fuel that is generated within the pump.
It has been previously shown that the stress concentrations can be reduced somewhat by shaping the intersection at the end of one passage in the region at which it intersects the other passage, for example by radiusing the intersection. Radiusing the intersection reduces the presence of sharp features and thin regions of material at the intersection, which contribute to stress concentrations. A radiused intersection can be achieved by, for example, electrochemical machining or abrasive polishing of the intersection.
As engine technology develops, there is a requirement to increase the pressure at which fuel is injected to the engine, and correspondingly the components of the fuel injection system, including the pump, must be further improved with respect to the pressure at which they can be reliably used.
Against this background, it would be desirable to provide a component having intersecting passages in which the stress concentrations at the intersection between the passages are further reduced in comparison to previously known intersection shapes.